1. Field of the Invention
The present invention relates to a silent chain power transmitting apparatus with no or a low mechanical wear generated between a silent chain and two or more sprockets and capable of operating with low noise.
2. Description of the Related Art
FIG. 6 is a diagram showing a configuration of a sprocket wheel and a silent chain (or an endless silent chain) comprising a plurality of link plates in a conventional silent chain power transmitting apparatus. FIG. 7 is a diagram showing a configuration of the link plates in the silent chain of the conventional silent chain power transmitting apparatus. In FIG. 6 and FIG. 7, reference character 110P designate a silent chain and 120P denotes the sprocket wheel having a plurality of teeth 122. The silent chain 110P is made up of a predetermined number of link plates 111A, 111B, 111C, . . . which are connected together through connecting pins 116 in endless form. Each link plate has a pair of teeth 112 and a pair of pin holes 115. Each link plate is connected together through each connecting pin 116 inserted into the corresponding pin hole 115. FIG. 6 and FIG. 7 show the link plates 111A, 111B, and 111C as a part of the entire of the link plate.
As shown in FIG. 6, each tooth 112 of the silent chain 110P is formed in a same configuration, each tooth 112 has an inside flank 113 and an outside flank 114. The inside flank 113 and the outside flank 114 are profiled by a straight line.
In FIG. 6 and FIG. 7, reference character PL designates a chain pitch line. The chain pitch line PL is a straight line connecting the center of each connecting pin 116 inserted into the corresponding pin hole 115 of each link plate 111A, 111B, 111C, . . . . Reference character P denotes a pitch of the silent chain, and Ψ is 2π/N radian, where π is a ratio of the circumference of a circle to its diameter, and N is the number of the teeth of a sprocket wheel (not shown in FIG. 6).
As shown in FIG. 6 and FIG. 7, the sprocket wheel 120P in the conventional silent chain power transmitting apparatus has a predetermined number of the teeth 122, each of which is meshed with the corresponding tooth 112 of the link chain of the silent chain 110P. Each tooth 122 of the sprocket wheel 120P is profiled by an involute curve. That is, each tooth 122 is an involute tooth.
In the configuration of the conventional silent chain power transmitting apparatus described above, the power of the sprocket wheel 120P as a driving side is transmitted to another sprocket wheel 120P as a slave side by meshing the teeth 112 of each link plate 111A, 111B, 111C, . . . of the silent chain 110P with the corresponding teeth 122 of the sprocket wheels 120P according to the revolution of the sprocket wheel 120P as the driving side.
In the conventional silent chain power transmitting apparatus described above, each of the inside flanks 113 and the outside flanks 114 of each link plate 111A, 111B, 111C, . . . is profiled by the linear shape, and each tooth 122 of the sprocket wheel 120P is profiled by the involute shape curve. The contact between the teeth 122 of the sprocket wheel 120P and the inside flanks 113 and the outside flanks 114 of the link plates 111A, 111B, 111C, . . . causes to increase both a relative of curvature and a slip ratio. The conventional silent chain power transmitting apparatus involves several drawbacks that the surface stress at the contact area is high so that the mechanical wear is generated between a link plate and a sprocket wheel.
Generally, the link plates 111A, 111B, 111C, . . . are made up of quenched steel to avoid rupture of a link chain. On the other hand, the sprocket wheel 120P is made up of steel or sintered metal. However, because the sintered metal is lower in mechanical property such as tensile strength and bending strength than the steel. Therefore it is difficult to keep the wear resistance of the sprocket wheel when the link plate made up of quenched steel and the teeth of the sprocket wheel made up of quenched sintered metal are meshed together. And it is expensive to apply high grade material to the link plate and/or the sprocket wheel on the purpose to avoid the above drawbacks.
In addition, although the silent chain power transmitting apparatus generates a relatively low driving noise when compared with the noise generated by the roller-chain power transmitting method, there is a strong demand to further reduce the driving noise.